1. Field of the Invention
This invention relates to a cordless telephone apparatus and more particularly to a cordless telephone apparatus in which a connection device generates a call or ringer tone when there is an incoming call from a subscriber's line during power stoppage.
2. Description of the Related Art
FIG. 5 schematically illustrates a cordless telephone apparatus.
In FIG. 5, a subscriber's line 1 is connected to a connection device 2 which is supplied with power from a commercially available power source 5. A cordless telephone 3 is connected to the connection device 2 via a radio circuit. A main telephone 4 is connected in parallel with the connection device 2. If there is an incoming call signal on the subscriber's line 1 from a telephone office, the connection device 2 detects it and connects the telephone 3 and the connection 2 via the radio circuit to thereby cause the telephone 3 to generate a ringer tone. When the connection device 2 is not connected with the telephone 3 via the radio circuit, however, the telephone 3 does not generate a ringer tone.
One could conceive a structure of the connection device 2 as shown in FIG. 6 in which if the connection device 2 is not connected with the telephone 3, a speaker 16 of connection device 2 is rung. Namely, in FIG. 6, if there is an incoming call on the subscriber's line 1, this call is detected by a rectifier 13 and a detector 14. The output from the detector 14 causes a control circuit 10 to drive a transmitter 7 and a receiver 9 to thereby establish a radio circuit between the connection device 2 and the telephone 3. This causes the call signal on the subscriber's line 1 to be delivered via a hybrid circuit 6 and a transmitter 7 to a synthesizer 8 from which the signal is carried on a carrier and transmitted via an antenna 11 to the telephone 3. This signal drives a sounder, not shown, of the telephone 3 to cause a ringer tone to be generated. A signal from the telephone 3 is received by an antenna 12 and applied to a receiver 9 whereupon the signal is demodulated by a signal from the synthesizer 8 and transmitted via the hybrid circuit 6 to the subscriber's line 1.
If no radio circuit is established between the connection device 2 and the cordless telephone 3 for some reason although there is an incoming call on the subscriber's line 1, the output of the detector 14 is delivered from the control circuit 10 via an amplifier 15 to a speaker 16 to thereby cause the speaker to produce a ringer tone. The control circuit 10 is driven with power supplied from the power source 5 to control the transmitter 7, synthesizer 8, receiver 9 and amplifier 15.
If no radio circuit is established between the connection device 2 and the telephone 3 although there is an incoming call on the subscriber's line 1, and a ringer tone is produced from the speaker 16 of the connection device 2, the main telephone 4, branching from the subscriber's line 1, responds to the incoming call. Therefore, in this case, the main telephone 4 is set in advance so that no ringer tone rings therein.
If the power source 5 stops supplying power in the conventional telephone apparatus, the control circuit 10 of the connection device 2 does not work. Under this condition, although there is an incoming call on the subscriber's line 1, no radio circuit is established between the connection device 2 and the telephone 3 because the control circuit 10 does not work, so that the telephone 3 does not produce a ringer tone. Since the control circuit does not work, it cannot deliver a signal to the amplifier 15, so that the connection device 2 does not produce a ringer tone either. Since the main telephone 4 is set in advance so that no ringer tone rings, the main telephone 4 does not produce a ringer tone either. Eventually, although there is an incoming call on the subscriber's line 1, none of the connection device 2, cordless telephone 3 and main telephone 4 produces a ringer tone. Namely, although there is an incoming call during power stoppage, it cannot be noticed at all.
One could conceive a structure in which the main telephone 4 is released from its non-ringing state so as to produce a ringer tone. In this case, however, both the telephones 3 and 4 produce a ringer tone, which is not desirable.